This silicone or thermoplastic rubber insert is produced by moulding. It comprises a top part of predetermined thickness in which a cross-shaped cut is made after moulding.
The cross-shaped cut creates four flaps which when frontally resting one against another hermetically close the container, whereas when a is pressure exceeding a certain threshold value is present in the container they flex outwards to hence free a dispensing port.
The drawback of this known art is that if the product to be dispensed contains sticky components, the front edges of the flaps can stick together and become difficult to open, necessarily requiring more pressure.
A further drawback of the known art is that when the flaps move into their closure position they frontally press against each other to form a hermetic seal which does not allow air to enter the container.